The present invention relates to a vacuum film deposition apparatus such as a vacuum evaporation apparatus. The invention more specifically relates to a vacuum film deposition apparatus capable of advantageously preventing a film-forming material from being deposited at undesired positions on the inner wall or other portion of a vacuum chamber even in the case of forming a thick film.
A radiation image detector which records a radiation image by first allowing a radiation (e.g. X-rays, α-rays, β-rays, γ-rays, electron beams or uv rays) to pass through an object, then picking up the radiation as an electric signal has conventionally been used in such applications as medical diagnostic imaging and industrial nondestructive testing.
Examples of this radiation image detector include a solid-state radiation detector (so-called “flat panel detector” which is hereinafter abbreviated as “FPD”) that picks up the radiation as an electrical image signal, and an X-ray image intensifier that picks up the radiation image as a visible image.
FPDs are operated by one of two methods, direct conversion method and indirect conversion method; in the direct method which involves the use of a film of photoconductive material such as amorphous selenium and a thin film transistor (TFT), electron hole pairs (e-h pairs) emitted from the photoconductive film upon incidence of a radiation are collected and the collected e-h pairs are read as an electric signal by the TFT, whereby the radiation is “directly” converted to the electric signal; in the indirect method, a phosphor layer (scintillator layer) which is formed of a phosphor that emits light (fluorescence) upon incidence of a radiation is provided such that it converts the radiation to visible light, which is read with a photoelectric transducer, whereby the radiation “as visible light” is converted to an electric signal.
In the FPDs adopting the direct method, films of photoconductive material such as amorphous selenium are formed by vacuum film deposition methods including vacuum evaporation.
In vacuum evaporation, vapors of a film-forming material come in contact with the inner wall of a vacuum chamber or a substrate holding means for holding a substrate, causing a film to adhere thereto. When having deposited to a large quantity, such film having adhered to other portions than the substrate forms particles (small flakes), which may adhere to a film formed by vapor deposition or the substrate, or be incorporated into the vapor-deposited film, thus causing quality degradation.
Therefore, vacuum evaporation apparatuses prevent films from being undesirably formed in the respective portions of the vacuum evaporation apparatuses as exemplified by the vacuum chamber inner wall and substrate holding means (substrate carrier) by providing a deposition preventing plate for preventing evaporating vapors from reaching undesired areas as described in JP 5-70931 A or by providing a deposition preventing plate surrounding the vacuum chamber inner wall or a deposition preventing plate for preventing a film from being deposited onto the substrate carrier.
The deposition preventing plate is detachably mounted in such vacuum evaporation apparatus (vacuum chamber). After the end of film deposition, the deposition preventing plate is detached from the apparatus for the maintenance work and washed, then the washed deposition preventing plate is mounted again in the apparatus, thus preventing deposition of a large quantity of film material thereonto and quality degradation due to the aforementioned particles.